White spots on your nails does not mean you have a calcium deficiency.
When you see white spots on the nail the most common myth is to think you have a calcium deficiency followed by a zinc deficiency. The truth is white spots are harmless and very common. they are more then likely a sign of trauma to the nail plate or matrix, it is just like folding a piece of clear plastic it leaves a white mark.
The nails are what separate the mammals from the primates.
Most mammals have claws to help them with their daily tasks, fingernails are something that distinguish primates from the rest of the group.
There is real a reason why we can't stand nails on a chalkboard.
The reason is because the noise hits a frequency that is naturally amplified by the shape of our ear which makes just the thought enough to make us cringe.